[Antennaware] Height

[Fabio IZ4AFW]

Hi all,
    I am planning to erect a 12 m tower on the roof of my house (which is 
about 13 m high HI).
Now, when I go into antenna modeling, which height should I consider? 12 
meters or 25 meters?
In other words, the antenna will be about 25 meters high from the (real) 
ground, but only 12 from the roof (which is not very big, about 10x10 
meters)...which height I have to consider in NEC?
I am planning a horizontal polarized antenna (probably yagi) for HF coverage.
Thanks, all the best
73
Fabio IZ4AFW


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